Stereophonic phonograph transducer



J A: Xff'ff y s 51635.55 J Oct. 19, 1965 E. C. MUNK 3,213,207

STEREOPHONIC PHONOGRAPH TRANSDUCER v2 Sheets-Sheet l Filed March 4, 1959 INVENTOR NNO COERT MUN K BY a il fe. l-

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STEREOPHONIC PHONOGRAPH TRANSDUGER Filed March 4, 1959 2 Sheets-Sheet 2 mi 53 24 QW l mms3 Fama NVENTOR NNO COER T MU NK BY f ,Z il# AGENT 3,213,207 STEREOPHONIC Pl-IONUGRAPH TRANSDUCER Enno Coert Munk, Eindhoven, Netherlands, assignor to North American Philips Company, lac., New York, N.Y., a corporation of Delaware Filed Mar. 4, 1959, Ser. No. 797,979 Claims priority, application Netherlands, Mar. 20, 1958, 226,665 4 Claims. (Cl. 179-160.41)

This invention relates to transducers for use in devices for recording or reproducing, with the aid of a common recording or reproducing member, a groove-shaped registration track in which two signals having different directions of vibration are recorded simultaneously.

In the known devices of this type two separate transducers are used, each for one of the signals. In order to enable the two signals to be recorded or reproduced simultaneously, the transducers must be connected ltogether by a coupling member. The part of this coupling member situated between the point of engagement of the recording or reproducing member and one of the two transducers must have the property of being rigid for one direction of vibration and yielding for the other direction of vibration, while the part lying between said point of engagement and the other transducer must have the reverse property. Thus Vthe coupling member serves to separate the double information.

The transducer in accordance with the invention iS characterized in that it comprises at least two parts which are connected together without the use of a coupling member, each part responding at least substantially to only one of the two directions of vibration. Thus the information is separated by the transducer itself without employing the coupling4 member of the known devices which of necessity are comparatively complicated. Hence, a feature of the device according to the invention is that it uses only a single transducer. The said parts of this transducer can be obtained by electrical and/or mechanical means without the use of a coupling member, as will be described more fully hereinafter.

The above-mentioned two signals may be a normal acoustic signal and a reverberant signal or a normal acoustic signal and a signal including various acoustic effects, for example echo effects, or two stereophonically associated acoustic signals. Alternatively, one signal may contain high frequencies and the other low frequencies f an acoustic signal train so that the depth of the initial sound image can be reproduced. Furthermore the two lsignals may be stereoscopically associated television signals.

The transducer itself may consist of a tubular body of ceramic material, for example piezoelectric barium titanate, to which bending stresses are applied and the inner and outer circumferences of which are provided with electrodes which serve to supply or derive the signal voltages and extend in the direction of length of the body. Electrodes are provided on parts which have been rendered responsive to the two signal voltages, i.e. these parts are prepolarized so that the direction of the remanent polarization is at right angles to the outer surface of the body. In the adjoining parts the directions of polarization are different, preferably at right angles to each other, while the two signal voltages are erich derived from, or supplied to, at least one outer electrode and, as the case may be, a corresponding inner electrode. Thus the two parts are formed by electrical means.

In a particular embodiment of this transducer, in which the body in the parts rendered responsive to the signal voltages is prepolarized in two ditlercnt directions which preferably are at right angles to each other, each of the two signal voltages is supplied to, or derived from a pair 3,213,207 Patented Oct. 19, 1965 Ecc of diametrically opposed outer electrodes, which constitute one terminal, and to or from a corresponding pair of interconnected inner electrodes, which form the other terminal. Advantageously the transducer'is designed so that the two signal voltages have a common inner electrode which covers the entire inner circumference of the body. The manufacture of such a transducer is particularly important from a technological point of view.

In another embodiment of the transducer shaped in the form of a tubular body, in which the body is prepolarized in the different parts -in directions away from and towards the centre lines of the body, each of the two signal voltages is supplied to or derived from an outer electrode, which forms one terminal, and the diametrically opposed outer electrode, which forms the other terminal, the corresponding diametrically opposed inner electrodes being directly interconnected. Thus a transducer is obtained with doubled sensitivity in that the two diametn'cally opposed parts of the transducer which are rendered responsive to one and the same signal, are connected in series. In a practical embodiment of this transducere the outer electrodes intended for one signal are axially displaced with respect to the outer electrodes for the other signal so that the outer electrodes do not overlap each other in this direction. This permits combining an inner electrode which covers the entire inner circumference of the body with each pair of outer electrodes. These inner electrodes must be separated axially. Thus the elements can be provided with inner electrodes by a comparatively simple technological method. The same technical advantage is obtained automatically in the firstmentioned embodiment in which one inner electrode can be used irrespective of the relative axial positions of the pairs of outer electrodes.

If in the above-described cases the pairs of outer electrodes are provided on the transducer axially displaced with respect to each other, the transducer can be made in one piece or it can be built up from two such bodies which are mechanically connected together without the use of a separate coupling member so as to be axially aligned but rotated relatively to each other through a certain angle, preferably an angle of Such transducers can be manufactured not only from ceramic piezo-electric material, such as BaTiO3, but also from other materials having piezo-electric properties, such as natural quartz, or from synthetic piezo-electric materials, such as synthetic quartz, Rochelle salt, ADP. These tubular transducers also must be subjected to bending stresses only in the device in accordance with the invention. Por this purpose, in a transducer made of BaTiOs the tubular body is prepolarized in a direction at right angles to the outer surface of the body. In order to enable a tube of quartz or Rochelle salt to vhave a bending stress applied to it, the tube must be cut from the material so that one of the useful crystallographic axes lies in a plane at right angles to the centre line of the tube.

The transducer in accordance with the invention can consist not only of tubular bodies, but also of plate-shaped bodies which are likewise connected together without separale coupling members. To this end two plate-shaped members are connected together so as to be in line with one another axially but at right angles to one another radially. These transducers can also be made from a ceramic piezo-electric material, such as BaTiO3, in which event a bending stress only is applied to them, or f-rom a material having piezo-electric properties, such as natural quartz, synthetic quartz, Rochelle salt, and the like, in which event theycan be subjected either to bending stress or to torsion. In order to enable a plate of Rochelle salt to be subjected to torsion an cut is taken from the material, while if a bending -stress is to be applied to the plate, a 45 X-cut" is taken from the material.

When the bodies are made of Rochelle salt, they can be united to form a single transducer by securing the tubes or plates together by means of an adhesive, and when the bodies are made of ceramic material, they can be united by soldering or by sintering them to each other during the manufacture of the plates. In these cases also the two parts which each substanitally respond to two different directions of vibration, are united to form a single transducer by mechanical means.

The invention will be described with reference to the accompanying drawings, in all figures of which similar reference characters relate to like parts, and in which:

FIG. 1 shows the manner in which a tubular bodyl of BaTiO3 for a transducer in accordance with the invention can be biased,

FIG. 2 shows the body prepolarized in this manner which can be used as a transducer in accordance with the invention,

FIG. 3 shows a modification of the manner in which the body in FIG. 1 is prepolarized,

FIG. 4 shows the transducer manufactured by this method,

FIG. 5 shows a practical embodiment of the transducer of FIG. 2, and

FIG. 6 shows a practical embodiment of the transducer of FIG. 4,

FIG. 7 shows parts which respond to the signal voltages in the form of tubular bodies which are attached to each other by an adhesive,

FIG. 8 shows a transducer in which the parts shaped in the form to tiattened tubular bodies are bonded to each other by adhesive,

FIG. 9 shows a transducer comprising plate-shaped parts to which a bending stress is applied,

FIG. 10 shows a transducer comprising plate-shaped parts which are subjected to torsion, and finally FIG. 11 is a sectional view of the transducer of FIG. 10 taken along the line XI-XL FIG. 1 is a cross-sectional view of a tubular body shaped in the form of a circular hollow cylinder 1. This body is made of ceramic piezo-electric material, for example BaTiO3. At several points on the outer and inner circumference of the body, electrodes 2 to 9 are provided which extend in the direction of the length of the body and to which prepolarizing voltages can be applied. When the positive terminal of the polarizing voltage supply is connected to the outer electrodes 2 to 5 and the negative terminal to the inner electrodes 6 to 9, there are produced four parts in the body which have a remanent polarization at right angles to the outer surface and which in pairs respond to signal voltages having different directions of' vibration. The parts between the electrodes 2, 6 and 4, 8 are polarized according to arrows 10 and the parts between the electrodes 3, 7 and 5, 9 are polarized according to arrows 11, the arrows of each pair 10 and 11 being diametrically opposed. A transducer made in this manner can be used in a device for recording or reproducing, by means of a common recording or reproducing member, a grooveshaped registration track in which two signals having different directions of vibration are recorded simultaneously. To this end the body may be fixed at one end in known manner and be provided at the other end with a recording or reproducing member. If, as is shown in FIG. 2, one signal (the .1c-signal) is connected through an amplier 12 to the electrodes 3 and 5 and the other signal (the y-signal) through an amplifier 13 to the electrodes 2 and 4, while the inner electrodes 7, 9 and 6, 8 respectively are directly interconnected, the variations of the x-signal will cause the body to bend in a vertical plane and the variations of the y-signal will cause it to bend in a horizontal plane. Thus the .vc-variations can be used to provide vertical modulation and the y-variations to provide lateral modulation of the groove. When the modulations in the groove are to be reproduced, the process is reversed, the double information in the groove being again Split UP in tWO Separate Cil signals which are each supplied by one of the responsive parts to the associated amplifier 12 or 13 respectively. In contradistinction to the known devices provided with a coupling member which serves to separate the double information after the groove-shaped registration track has been followed, here the transducer itself acts to separate the information in reproduction and to combine it in recording.

It will be appreciated that if only two adjacent parts are` provided in the body or employed, which have different directions of polarization, the transducer operates in the same manner but with halved sensitivity. Obviously in this event the inner electrodes must not be interconnected.

In FIG. 3 prepolarization is effected so as to produce two directions of polarization, one in the direction of arrows 14 and the other in the direction of arrows 15. Unlike the arrows of FIG. 1, here the two arrows of each pair 14 and 15 respectively point in the same direction. common inner electrode 16 (see FIG. 4 also) can be connected to earth, one terminal of the xand y-voltages being likewise connected to earth by way of the associated amplifier 12 and 13 respectively, while the other terminal of the xand y-Voltages is connected to the outer electrodes 3, 5 and 2, 4 respectively. Obviously, in the latter case the second terminal of the xand y-voltages can also be connected to one of the two outer electrodes 3, 5 and 2, 4 respectively. Furthermore the inner electrode may be split up in four separate electrodes. However, it will be yappreciated that it is preferable technologically to provide a common electrode internally.

Even for the transducer of FIG. 2 the inner circumference of the tube can be provided with one electrode throughout the circumference, Since, however, the tube is prepolarized in a direction from or towards the center line of the body, the inner electrodes must in any case be separated. In the transducer shown in FIG. 5 this separation is effected by the outer electrodes 3, 5 for the :c-signal being `airially displaced relatively to the electrodes 2, 4 for the y-signal so that the outer electrodes do not overlap in this direction while the inner electrode, which covers the entire inner circumference, is gapped at this transition zone.

Obviously the pairs of outer electrodes can also be parted in the transducer of FIG. 4. Then the transducer shown in FIG. 6 is produced. One terminal of the amplier of the x-signal is connected to the outer electrodes 3 and/or 5 and one terminal ofthe amplier of the y-signal is connected to the outer electrodes 2 and/or 4, the inner electrodes extending throughout the length of the tube and being connected to the outer terminals of the amplifiers or to earth, in which latter event the said two other `amplifier terminals must also be earthed.

The transducer in accordance with the invention can be manufactured from a body which is an integral structure, the parts which respond to the two signal voltages being produced electrically (by prepolarization) but such a transducer can also be manufactured from at least two separate parts which are united to form one transducer by mechanical means.

In FIG. 7 the said parts are two tubular bodies 17 and 18 which are aligned axially but are rotated with respect to each other so that the pair of outer electrodes 3, 5 for the x-signal is shifted through relatively to the pair of outer electrodes 2, 4 for the y-signal. In the same manner the transducer according to FIG. 6 can be obtained by mechanically joining two tubular parts, in which event one terminal of the amplifier of the x-signal is connected to the electrode or electrodes 3 and/or 5 and one terminal of the amplifier of the y-signal is connected to the electrode or electrodes 2 and/or 4, while the other terminals of the amplifiers can be connected to earth when the inner electrode is likewise connected to earth. Such mechanically joined tubular bodies which are subjected to bending stresses, can be made from a material such as BaTi3, from quartz, Rochelle salt, or from similar synthetic materials. In the case of Rochelle salt the two parts 17 and 1S can be bonded by means of an adhesive; in the case of BaTiO3 by soldering or sintering at 19.

FIG. 8 shows diagrammatically a transducing device comprising a transducer which consists of two mechanically joined parts 20 land 21 the cross-sections of which are not truly circular. One end of the transducer is clamped in the usual manner and the other end is provided with a recording or reproducing member 22. Alternatively, the transducer can be clamped at both ends, the recording or reproducing member being provided midway between the ends.

FIG. 9 shows diagrammatically a transducing device comprising a transducer the parts of which consist of plate-shaped members 23 and 24 to which a ben-ding stress is to be applied. Suitable materials for manufacturing these parts are Ba1`i03, quartz, Rochelle salt, and the like. These parts are mechanically united to form one transducer by joining two members in line .with one another axially and at right angles to one another radially. If BaTiOa is used as the material for the plate-shaped members, each member 23 and 24 comprises two plates attached to one another through an intermediate layer, the direction of polarization being at right angles to the main faces.

FIG. shows diagrammatically a transducing device comprising a transducer the parts of which are likewise plate-shaped members (25, 26) which are mechanically joined in line with one another axially and at right angles lto one another radially. In order to enable the members to be subjected to torsion, the plates 25 and 26 are each provided with two forked guiding members 27, 28 and 29, 30 respectively (see FIG. 1l). Thus a three-point suspension is obtained so that, when the part 25 is twisted by the action of a variation of the x-voltage, the plate 26 is rigid for this variation and can only perform a movement along the line joining the guide members 29, 30. Conversely, the plate 25 is rigid for a variation of the y-voltage and will only move along the line joining the guide members 27, 28, the plate 26 being twisted.

While the invention has been described in connection with specific examples and embodiments, other modifications thereof will be apparent to those skilled in this art without departing from the spirit and scope of the invention as defined in the appended claims.

What I claim is:

1. A transducer for selectively recording and reproducing oscillations corresponding to variations in two different directions in a groove comprising a member adapted to oscillate in said groove in accordance with said variations, and an element for selectively converting the oscillations into two separate electrical signals each corresponding to one of the directions of oscillation and for converting a composite signal into two oscillations each having a different direction, said element comprising at least two tubular bodies of ceramic piezoelectric material mechanically joined together in an axial direction, each of said bodies being polarized in a direction at right angles to the outer surface of the body with adjoining bodies having diterent directions of polarization, each of said bodies having electrodes positioned on opposing inner and outer surfaces between which a signal is selectively applied or obtained.

2. A transducer as claimed in claim 1 in which the bodies are joined by an adhesive.

3. A transducer as claimed in claim 1 in which the directions of polarization of adjoining bodies are at right angles to one another.

4. A transducer for selectively recording and reproducing oscillations corresponding to variations in two different directions in a groove comprising a groove-following member adapted to oscillate in said groove in accordance with said variations, and means for applying to and deriving two broad spectrum signals from said groovefilling member including an element for selectively converting the oscillations in said groove into two separate electrical signals each corresponding to one of the directions Of oscillation and for converting two broad spectrum electrical signals into two oscillations each having a different direction, said element comprising a tubular body of ceramic piezoelectric material, a pair of electrodes extending axially along the inner surface of said body, and at least two pairs of longitudinally extending electrodes positioned on diametrically opposite portions of the outer surface of said body which have been prepolarized with the directions of remanent polarization extending in opposite directions at right angles to the axis of the body and with adjoining portions of said body having directions of polarization at right angles to one another, signals being derived from and applied to corresponding opposing electrodes. the outer electrodes for one signal being axially displaced from the outer electrodes to which another signal is applied, the inner electrodes being spaced in the axial direction a distance corresponding to the spacing between respective pairs of outer electrodes.

References Cited by the Examiner UNITED STATES PATENTS 2,439,499 4/48 Williams et al 310-9.8 X 2,614,143 lO/52 Williams 179-100.41 X 2,834,158 5/58 Petermann 179-100.4l X 2,880,334 3/59 Mason 179-100.41 2,928,059 3/60 Petermann 179-100.41 X 2,944,117 7/60 Gray 179-100.41 2,979,573 4/61 Kuhn 179-100.41`

IRVING L. SRAGOW, Primary Examiner.

L. MILLER ANDRUS; NEWTON N. LOVEWELL,

ELI I. SAX, Examiners.

UNITED STATES PATENT OFFICE CERTIFICATE OE CORRECTION Patent No 5 ,213, 207 October 19 1965 Enno Coert Munk s in the above numbered patthat error appear Patent should read as ent requiring correction and corrected below read groove-fllowng Ine 20, before for "BaTS" for "groove-filling Column 4, column 5, line I,

Ines I9 and 20,

Signed and sealed this 31st day of May l966 (SEAL) Attest: ERNEST W. SWIDER EDWARD I. BRENNERY Commissioner of Patents Attesting Officer 

1. A TRANSDUCER FOR SELECTIVELY RECORDING AND REPRODUCING OSCILLATIONS CORRESPONDING TO VARIATIONS IN TWO DIFFERENT DIRECTIONS IN A GROOVE COMPRISING A MEMBER ADAPTED TO OSCILLATE IN SAID GROOVE IN ACCORDANCE WITH SAID VARIATIONS, AND AN ELEMENT FOR SELECTIVELY CONVERTING THE OSCILLATIONS INTO TWO SEPARATE ELECTRICAL SIGNALS EACH CORRESPONDING TO ONE OF THE DIRECTIONS OF OSCILLATION AND FOR CONVERTING A COMPOSITE SIGNAL INTO TWO OSCILLATIONS EACH HAVING A DIFFERENT DIRECTION, SAID ELEMENT COMPRISING AT LEAST TWO TUBULAR BODIES OF CERAMIC PIEZOELECTRIC MATERIAL MECHANICALLY JOINED TOGETHER IN AN AXIAL DIREC- 